Testing Chevrolet Performance’s New 4L75-E Transmission At Drag Week

Unless you’ve been hiding under an oil drum somewhere, you’ve no doubt heard about Larry Dixon’s ’66 Nova and the process of modernizing the car that began last year. Larry and his guys put a lot of work into the Nova, and then survived the gauntlet called Drag Week in 2016. But, in case you were stuck under that oil drum, you can check out all the articles about the build right here.

Larry had a little fun at this year’s Drag Week. He gussied-up his Nova and paid homage to one of his heroes, Da Grump.

The transmission survived the abuse of testing. The pinion gear? Not so much.

But now, the folks at Chevrolet Performance have announced a new crate transmission that is available as a stand-alone unit, or with their Connect & Cruise offerings. We’re sure this will definitely make a lot of hot rodders very happy: The 4L75-E Supermatic. This new automatic transmission has two very important aspects that make it stand out above many other transmissions. For starters, it’s as durable as a 4L80-E or Turbo 400, but, it comes in a package that is smaller and comparable to a 4L60-E or 700R4 automatic transmission.

I sheared the pinion shaft on Thursday… We had the car up and running on Saturday and made Tech in Cordova, on Sunday – Larry Dixon

That means the small-ish size and large torque handling capabilities make it the perfect high-horsepower capable hot-rodders dream transmission. It is no secret that the 4L60-series transmission is an absolute workhorse fitted into many late-model GM vehicles. It has been used in, literally, millions of cars and trucks throughout the 1990s and early 2000s. Its four-gear package includes an overdrive and lock-up converter, and shares equivalent dimensions with the older 700R4. It was a great transmission when used in “pedestrian” applications, but when enthusiasts wanted an upgrade, the 4L80-E was the next step.

Like the 4L60-E, it too is a four-speed automatic, but it varies in that it is internally based on the Turbo 400. Externally, the 4L80-E is a bulging monster. Its larger size means that transplanting it into a classic conveyance typically requires a modified transmission tunnel to make room for the bigger case. That means cutting the floor of your classic and making a new tunnel area. “I was fortunate in that the 4L85-E required no tunnel clearance on the original install,” Larry recalled. It was close, but the custom engine and transmission mounts helped keep the driveline angles in check.

One Tough Overdrive

Getting back to the 4L75-E, with a rated torque sustainability of 650 lb-ft – and we’re guessing that Chevrolet is being conservative, it will definitely be the new go-to transmission for many enthusiasts. The above qualities are exactly why Larry decided to install this new transmission in his ’66 Nova.

We all know that Larry’s Nova has already been fitted with a Chevrolet Performance Supercharged LT4 and a 4L85-E transmission, so what’s the big deal with putting this new, dimensionally smaller transmission in its place? If the bigger one fit, surely, the smaller one will as well. “When I installed the 4L85-E, I used a custom transmission crossmember from musclerods.com, as the late-model transmission’s mount is substantially rearward compared to the classic three speed auto. During the 4L75-E install, I used my initial crossmember that I had used with the previous Turbo 350 that was in the car from years ago. I believe that was originally for a Powerglide-equipped car. I put the Turbo 350 in the car way back in 1988, so my memory has faded a little from what I did back then, but regardless, now the car uses a factory crossmember,” Larry stated.

Although the SFI shields cover the 4L85-E, the larger size is still apparent.

Making the connection to the driveshaft is also a simple task. “It is the same as a Turbo 350, Powerglide, 4l60, 4l60-E, 700R4, and 200R4, a common 27 spline yoke is needed,” according to Curt Collins of Chevrolet Performance.

Now that we’ve covered the fitment discussion, we were curious if this new transmission would survive the same abuse as the larger 4L85-E did last year when Larry competed in Drag Week. That means the testing had to take place under the same grueling conditions. No problem, Larry was more than happy to oblige.

Now, we really would not be able to make an apple-to-apple comparison as far as track e.t. and such, because, let’s face it, some things are different between the two transmissions, and will most likely affect the e.t. Take for instance each transmission’s gearing. The 4L85-E features a 2.48 first-gear ratio while the 4L75-E delivers a 3.06.

That alone is substantial, but when you also figure in the 4L85-E’s 1.48 second gear vs. the 4L75-E’s 1.62, you can see what we mean. As a side note, the overdrive in the 4L85-E is 0.75, while the 4L75-E is 0.70. Coincidentally, since the difference in gearing did prohibit an even testing platform and when purchased alone, the 4L75-E does not come with a torque converter, Larry installed a torque converter from Yank with a 3,500-stall rating.

Larry assures us that the 4L75-E fits with no cutting of the floor, but the transmission shields did required some tunnel mods.

Never Say Die

Now that we have the technical stuff out of the way, let’s focus on the beating the 4L75-E received during Drag Week. The couple weeks leading up to the week-long torture test were a thrash to say the least. While the transmission swap was straightforward – a few mods were required, due to Larry needing to meet certain drag strip safety requirements. Those safety requirements were in the interest of driver safety. Take for instance the transmission and flexplate shields. According to the NHRA rule book, any vehicle running faster than 135 mph must meet the minimum requirements for 9.99-second vehicles. This means, if you run quicker than 135 mph with an automatic transmission, an SFI 4.1 transmission shield, 30.1 flexplate shield and a 29.1 flexplate must be used. Larry is planing to eventually achieve those quarter-mile numbers, so the cutting was required to the transmission tunnel; not because the 4L75-E wouldn’t fit, to the contrary, the transmission fit great, the safety shields – not so much.

Before Larry was to start the grueling test of Drag Week, he wanted to get some testing done just to make sure all was good with the Nova and the new transmission. But, we all know that things break when you’re racing, and they never break at an opportune time.

Take for instance the unplanned departure of a functioning rearend. During a test session the Thursday before the start of Drag Week, the rearend of Larry ‘s Nova decided to no longer be considered “functioning.” “I sheared the pinion shaft on Thursday. As soon as we got back to the shop, I ordered one through Jegs and got it Friday. We had the car up and running on Saturday, and made tech in Cordova, on Sunday,” Larry told us.

The car is getting quicker, and Larry got his first 10-second time slip during the event. He told us it took a lot of pedaling to get there, but the small tire situation is being addressed.

This was the second year in a row that Larry subjected his ’66 Nova to the abuses of a week-long drag test session, but the outcome was worth it. As for Drag Week, the car drove flawlessly – on and off the track. “I love that it gets 22 mpg and it’s a verified 10-second street car. The one problem I did have, was working with the lower first gear in the 4L75-E. The ratio caused a traction issue with my 9.5-inch drag radials. That’s not to say that it’s the transmission’s fault. It now gets boost quicker than before because of it,” he quipped. But, he does have a remedy for that situation. “I am having a set of Rally wheels made with a 1/2-inch more backspacing, and that will allow me to fit a 10.5-inch wide rear tire on the car. That should give me better traction, which should allow for much quicker et’s. As for shifting, I just leave it in Third and let it shift itself.”

As Larry eluded, even after all the abuse that he inflicted upon the new 4L75-E, the proven performer even delivered a healthy 22 mpg during the jaunts between race tracks. So, not only did this new transmission survive the abuse of 10-second quarter-mile passes, it also made the drive between tracks financially pleasant since not many fuel stops were needed. All told, it’s hard to argue that the week of testing makes a great case for the durability of this new electronically-controlled Supermatic shift box.

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About the author

Randy Bolig

Randy Bolig has been working on cars and has been involved in the hobby ever since he bought his first car when he was only 14 years old. His passion for performance got him noticed by many locals, and he began helping them modify their vehicles.